mdh.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Anaerobic co-digestion of sludge and microalgae grown inmunicipal wastewater – feasibility study
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0002-0861-6438
Swedish University of Agricultural Sciences, Sweden.
Swedish University of Agricultural Sciences, Sweden.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0002-8034-4043
Show others and affiliations
2018 (English)In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 77, no 3, p. 682-694Article in journal (Refereed) Published
Abstract [en]

In this study a natural mix of microalgae grown in wastewater of municipal character was co-digested with sewage sludge in mesophilic conditions, in both batch and semi-continuous modes. The semicontinuous experiment was divided into two periods with OLR 1 (Organic Loading Rate) of 2.4 kg VS m3 d-1 and HRT1 (Hydraulic Retention Time) of 15 days, and OLR2 of 3.5 kg VS m3 d-1 and HRT2 of 10 days respectively. Results showed stable conditions during both periods. The methane yield was reduced when adding microalgae (from 200 ± 25 NmL CH4 g VSin-1 , to 168±22 NmL CH4 g VSin-1). VS reduction was also decreased by 51%. This low digestability was confirmed in the anaerobic batch test. However, adding microalgae improved the dewaterability of the digested sludge. The high heavy metals content in the microalgae resulted in a high heavy metals content in the digestate, making it more difficult to reuse the digestate as fertilizer on arable land. The heavy metals are thought to originate from the flue gas used as a CO2 source during the microalgae cultivation. Therefore the implementation of CO2 mitigation via algal cultivation requires careful consideration regarding thesource of the CO2-rich gas.

Place, publisher, year, edition, pages
2018. Vol. 77, no 3, p. 682-694
Keywords [en]
Biogas, dewaterability, Gompertz model, mesophilic, semi-continuous study, waste activated sludge
National Category
Renewable Bioenergy Research Water Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-37381DOI: 10.2166/wst.2017.583ISI: 000424765000013Scopus ID: 2-s2.0-85042218057OAI: oai:DiVA.org:mdh-37381DiVA, id: diva2:1162359
Projects
MAASICA-projektet
Funder
Knowledge FoundationAvailable from: 2017-12-04 Created: 2017-12-04 Last updated: 2018-07-20
In thesis
1. Co-digestion of microalgae and sewage sludge - A feasibility study for municipal wastewater treatment plants
Open this publication in new window or tab >>Co-digestion of microalgae and sewage sludge - A feasibility study for municipal wastewater treatment plants
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The increased emissions of anthropogenic greenhouse gases over the last 100 years is the reason for the acceleration in the greenhouse effect, which has led to an increase of the globally averaged combined land and ocean surface temperature of 0.85 °C between 1880 and 2012. A small fraction of the increased anthropogenic greenhouse gases originates from municipal wastewater treatment plants (WWTPs).

This doctoral thesis was part of a larger investigation of using an alternative biological treatment based on the symbiosis of microalgae and bacteria (MAAS-process (microalgae and activated sludge)). This solution could be more energy efficient and potentially consume carbon dioxide from fossil combustion processes and also directly capture carbon dioxide from the atmosphere and thereby reduce the addition of anthropogenic greenhouse gases to the air.

 The objective of the thesis was to explore the effects when the microalgae-derived biomass from the biological treatment were co-digested with sewage sludge. The results from these experimental studies were then used to evaluate the effects on a system level when implementing microalgae in municipal WWTP.

 Microalgae grown from a synthetic medium improved the methane yield with up to 23% in mesophilic conditions when part of the sewage sludge was replaced by the microalgae. The microalgae grown from municipal wastewater showed no synergetic effect.

 In the semi-continuous experiments the methane yield was slightly reduced when implementing the microalgae. Furthermore the digestibility of the co-digestion between sewage sludge and microalgae were lower compared to the digestion of sewage sludge.

 The digestates containing microalgal substrate had higher heavy metals content than digestates containing only sewage sludge. This could have a negative effect on the potential to use this digestate on arable land in future, due to strict limits from the authorities.  Filterability measurements indicated that the addition of microalgae enhanced the dewaterability of the digested sludge and lowered the demand for polyelectrolyte significantly.

 When a hypothetical MAAS-process replaced a conventional ASP-process the amount of feedstock of biomass increased significantly due to the increased production from the autotrophic microalgae. This increased the biogas production by 66-210% and reduced the heavy metal concentration in the digestate due to a dilution effect from the increased biomass production.

 The thesis demonstrates that microalgae in combination with bacteria from a MAAS-process can be a realistic alternative feedstock to WAS in the anaerobic digestion at a municipal WWTP. A few drawbacks need to be considered when choosing a MAAS-process as biological treatment.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2018. p. 96
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 262
Keywords
Microalgae, Anaerobic digestion, dewaterability, BMP-experiments
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-39154 (URN)978-91-7485-386-5 (ISBN)
Public defence
2018-06-18, Paros, Mälardalens högskola, Västerås, 13:00 (English)
Opponent
Supervisors
Funder
Knowledge Foundation
Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-06-04Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Olsson, JesperZambrano, JesúsSchwede, SebastianNehrenheim, EmmaThorin, Eva

Search in DiVA

By author/editor
Olsson, JesperZambrano, JesúsSchwede, SebastianNehrenheim, EmmaThorin, Eva
By organisation
Future Energy Center
In the same journal
Water Science and Technology
Renewable Bioenergy ResearchWater Engineering

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 60 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf